Book Online Demo

Check Your IQ

Try Test

Courses

Dropper NEET Course Dropper JEE Course Class - 12 NEET Course Class - 12 JEE Course Class - 11 NEET Course Class - 11 JEE Course Class - 10 Foundation NEET Course Class - 10 Foundation JEE Course Class - 10 CBSE Course Class - 9 Foundation NEET Course Class - 9 Foundation JEE Course Class -9 CBSE Course Class - 8 CBSE Course Class - 7 CBSE Course Class - 6 CBSE Course

Offline Centres

The angle of elevation of a jet fighter from a point A on the ground is $60 °$ . After a flight of 15 seconds, the angle of elevation changes to $30 °$ . If the jet is flying at a speed of $720 km / hr$ , find the constant height.

see full answer

Talk to JEE/NEET 2025 Toppers - Learn What Actually Works!

Real Strategies. Real People. Real Success Stories - Just 1 call away

An Intiative by Sri Chaitanya

2.59 km

3.59 km

4.59 km

5.59 km

answer is A.

(Unlock A.I Detailed Solution for FREE)

Ready to Test Your Skills?

Check your Performance Today with our Free Mock Test used by Toppers!

Take Free Test

Detailed Solution

Given that the angle of elevation of a jet fighter from a point A on the ground is

60 °

.
We have to find the constant height.
The value for the trigonometric identities can be evaluated by using the right-angled triangle the value for

tan θ

can be expressed as

tan θ = opposite adjacent

Suppose, B and C be the two positions of the jet fighter and the constant height of the jet fighter be BE=CD=h.
Since the speed of jet fighter is

720 km / hr

Thus, the distance covered in 15 seconds is,

B C = 720 × 1000 × 15 3600 = 720 × 150 36 = 3000 m = 3 km

The required figure geometry is shown in the figure below,
Question Image

Then by using the figure geometry, in triangle BCA

tan θ = B E A E ⇒ tan 60 ° = h A E ⇒ 3 = h A E ⇒ A E = h 3

Similarly, in a triangle CDA

tan θ = C D A D ⇒ tan 30 ° = h A D ⇒ 13 = h A D ⇒ A D = h 3

A D = A E + E D ⇒ 3 h = h 3 + 3 ⇒ 2 h = 33 ⇒ h = 2.59 km

The constant height is 2.59 Km.
Therefore, the correct option is 1.

Watch 3-min video & get full concept clarity

Result Producing online coaching for JEE/NEET of south India

Largest All India Test Series for JEE/NEET

Best Books for IIT JEE

Best Books for NEET

How to Join IIT after 10th

Best Courses for You

JEE

NEET

Foundation JEE

Foundation NEET

CBSE

Get Expert Academic Guidance – Connect with a Counselor Today!